Abstract

Magnetic resonance spectroscopy (MRS) is a non-invasive technique to detect metabolites within the normal and tumoral tissues. The ability of MRS to diagnose areas of high metabolic activity linked to tumor cell proliferation is particularly useful for radiotherapy treatment planning because of better gross tumor volume (GTV) delineation. The GTV may be targeted with higher radiation dose, potentially improving local control without excessive irradiation to the normal adjacent tissues. Prostate cancer and glioblastoma multiforme (GBM) are two tumor models that are associated with a heterogeneous tumor distribution. Preliminary studies suggest that the integration of MRS into radiotherapy planning for these tumors is feasible and safe. Image-guided radiotherapy (IGRT) by virtue of daily tumor imaging and steep dose gradient may allow for tumor dose escalation with the simultaneous integrated boost technique (SIB) and potentially decrease the complications rates in patients with GBM and prostate cancers.

KEYWORDS:

This patient with a glioblastoma multiforme shows the voxel over the area of interest in the tumor over the sagittal T1 (A) and axial FLAIR (B) image. Magnetic resonance spectroscopy (C) shows an elevated choline peak (single arrow) and decreased creatine (double arrow) and N-acetyl aspartate (NAA) peaks (triple arrow), which is the typical pattern for tumor (Images courtesy of Dr. Ashok Srinivasan, University of Michigan).

This patient had a radical prostatectomy demonstrating two intra-prostatic adenocarcinoma in the pre-operative magnetic resonance spectroscopy areas suspicious for malignancy. These two gross tumor volumes could have been treated to a higher radiation dose (81 Gy) while the prostate received only 78 Gy with the image-guided radiotherapy technique, thus improving the chance for local control and decreasing the risk of long-term rectal damage. (A) The areas outlined in red showed the cancerous tissue in the right and left lobe in the prostate. (B) The areas outlined in orange had an abnormal CCr (choline+creatine/citrate) ratio suspicious for malignancy on pre-operative magnetic resonance spectroscopy. (Images courtesy of Dr. Shigeo Horie, Teikyo University, and Dr. John G. Delinasios, International Institute of Anticancer Research.)